The present invention writes generally to digitizing input devices and, more particularly, the present invention relates to the utilization of a magnetic random access memory (MRAM) device as a digitizing array within a digitizer apparatus.
Digitizer systems are well known to those skilled in the art. Typically, an electromagnetic array, or other type of system, is responsive to a stylus used by a user to enter data directly upon a grid and to control various computer functions by writing, sketching, or pointing the stylus against the digitizer array. Some embodiments locate the digitizer directly on the monitor; other embodiments separate the two devices. Usually, separate digitizers are utilized where a large work surface is needed compared to the size of the display device such as a monitor screen. Integrated digitizer and display devices are utilized where portability and size are important. As such, various types of computer systems utilize stylus-based technologies and may include portable systems, desktop systems, transportable, or terminal-based systems.
The integrated digitizer-display systems are integrated only in the sense that they are coplanar and are fitted together in a common device. They are not integrated in that a signal processor is required to convert the signals generated by the digitizer into display signals compatible with the display. Thus, additional circuitry and complexity are involved in even the simplest of digitizer-display systems that are integrated for direct input on the same display surface where the digitizer is located.
Several types of stylus input digitizing devices exist in the prior art. One type involves direct contact of a stylus tip against a capacitive-resistive array. As the stylus tip, such as a metal tip or even a user""s finger, is placed proximate a selected area of a digitizing pad, a capacitive-resistive circuit within the pad detects the placement of the stylus and computes its location according to well-known mathematical formulas of a grid-based array. Typically, the capacitive-resistive array is used over small areas in devices such as a portable digitizer screen or finger-sensitive mouse pad.
A second prior art system utilizes an electromagnetic digitizer that interacts with a magnetic-tipped stylus or electromagnetic field-generating stylus in entering data and performing actions desired by the user. The tip of the stylus interacts with the field on the digitizer to convey information and data from the user. Typically a grid of intersecting lines produces a field that can be either actively or passively modified by the field generated by the stylus. Crossing lines can sense the field of the tip to generate a responsive signal, or can produce a field altered by the stylus during interaction.
Another embodiment is that of a stylus having an RF transmitter to send signals to the digitizing array, which then detects the transmitted signals utilizing receiving circuits in the array. Alternatively, the pad locations may be coated and the RF signal generated by the stylus interact with the array and are received at a receiver within the stylus itself.
Further, an alternative embodiment may incorporate a light source, such as visible or infrared light placed within the tip of the stylus to reflect off the pad. The stylus uses an imaging device, such as a CCD camera, to detect optically the return signal, and hence the location where the stylus interacts with the digitizer. The system then processes and decodes the received signal and location in order to determine the appropriate information.
Each of these systems has had some success; however, each has limitations that make them difficult or undesirable to use. For example, the direct contact technology is subject to scratches and wear during normal operation and has low durability compared to other technologies.
The wire-grid electromagnetic technology is expensive to implement and requires many individual wires for greater resolution. Additionally, the electromagnetic digitizers typically require a planar magnetic material behind the wire-grid sensor to shield the system from stray magnetic effects. In portable uses, this makes the technology for the system implementing such technology heavier than necessary. In the light-based systems, the stylus needs to be corded to the digitizer array and the need for sophisticated electronics for producing the light source as well as the CCD camera must be incorporated and expanded to achieve such a stylus.
One disadvantage common to all the various types of prior art digitizing technologies is that the digitizing array must always be under power in order for interaction of the user""s stylus with the digitizer to be maintained. Further, the user must also save the information to long-term storage, such as the hard disk drive on the computing system, in order to preserve the content of the user""s stylus session. Furthermore, in portable devices, the same can be said that the user""s input must be stored in long-term memory and cannot be maintained on the digitizer, typically which is overlayed with the displayed system so that the user can keep the most recent information upon restart of the apparatus unless power is provided to preserve the information in memory.
Digitizing arrays have been mated with display systems in order to provide an easy method of drawing and viewing the results simultaneously. For example, a digitizing array may be overlayed with an indium tin oxide display panel such that if the user interfaces with the digitizer using the stylus, the images displayed immediately under the stylus as the user interacts therewith. This enables the user to interact with the screen as if interacting with real data or writing on an actual writing tablet using a pen. Such technologies always require the use of an input signal processor, which coordinates with the digitizer to receive the user""s input via electromagnetic pulses, light pulses, resistive interaction or the used system to process the signals for display on the display apparatus portion.
Accordingly, what is needed is an improved digitizing apparatus that has greater resolution than the prior art systems, is easier to manufacture, and is more durable during actual use. Further, what is required is a digitizer apparatus that can be integrated with a display device and that can be manufactured with such a display as an electroluminescence apparatus using the same processing methods and techniques.
According to the present invention, an integrated digitizing tablet with color display is disclosed. The digitizing tablet portion of the integrated digitizing tablet and display apparatus includes an array of magnetic random access memory (MRAM) cells that can be modified by at least one externally-applied magnetic field, wherein each memory cell has a magnetic bit that changes orientation upon the application of the externally-applied magnetic field to produce an electrical signal based on the orientation of the bit when an electric field is applied across the array. The display portion comprises an array of color pixel cells, each color pixel cell being selected from more than one color type and being coupled to one of the MRAM cells. The MRAM cell is operated to activate the coupled color pixel cell in response to the electrical signal produced by the MRAM cell. Typically, the color pixel cells are selected from the colors red, blue, and green in approximately equal ratios or may be selected from their complementary colors which would include cyan, magenta, and yellow. Any color scheme may be implemented and is not limited to merely three colors or be required to be more than two.